1. Field of the Invention
The present invention relates to a transmission state indicating system, and in particular, to a transmission state indicating system indicating pointer values for evaluating a transmission state of a communication network which uses, for example, an SDH (Synchronous Digital Hierarchy) system or a SONET (Synchronous Optical Network) system and which has a plurality of channels, at the same time corresponding to the respective channels.
2. Description of the Related Art
Recently, in the field of digital transmission, in order to transmit high capacity data by effectively using an existing network, a technique called a virtual concatenation (Virtual Concatenation: ITU-T G. 707) has been standardized in which high capacity data are divided and contained into a plurality of low capacity virtual containers (Virtual Container: VC), and after the low capacity data contained in the plurality of virtual containers are separately transmitted to a plurality of channels, and the data is correctly assembled and multiplexed, and then transmitted to another high capacity channel.
In this case, the respective channels configuring the existing network have respectively different transmission capacities and different transmission distances. Therefore, in order to stably carry out data transmission by the virtual concatenation technique, it is important to grasp in advance the transmission delayed amounts at the respective channels and the amount of variations in phases due to phase differences between the clocks of the respective channels at the low capacity channel sides and a clock of the high capacity channel at the multiplexed side, as pointer values for evaluating the transmission state of the communication network having the plurality of channels.
However, with respect to an existing wire communication network using the SDH/SONET transmission system as the base, currently, no transmission state indicating system has been known in which the delayed amount at the times of transmissions at respective channels and the amount of variations in phases due to differences between the clocks of the respective channels at the low capacity channel side and the clock of the high capacity channel, as pointer values for evaluating the transmission state of the communication network.
Note that, with respect to a mobile communication system, as disclosed in Jpn. Pat. Appln. KOKAI Publication No. 2000-36802 which is Patent document 1, a transmission state indicating apparatus in which a strength of a received CDMA signal and respective channels are indicated by associating with one another has been known.
The SDH transmission system is described in ITU-T G. 707 or the like.
The SONET transmission system is described in ANSI TI. 105 or the like.
However, the transmission state indicating apparatus as disclosed in the Patent document 1 indicates a strength of a radio wave in a case of using a mobile communication system due to radio communication, and cannot be applied to a case of using a wire communication network.
Accordingly, there are the problems that not only it is impossible to distinguish the pointer values which are required when high capacity data is divided into a plurality of virtual containers and transmitted by digital transmission via a wire communication network having a plurality of channels such as the SDH/SONET transmission system or the like, and which are for evaluating the transmission state of the communication network having the plurality of channels, i.e., the effect on the performance of a receiving apparatus due to the amount of variations in phases and the delayed amount, but also it is impossible to grasp in advance how large they are.
Note that, when the high capacity data is divided into a plurality of frames respectively having the low capacity containers and transmitted by digital transmission via the wire communication network having a plurality of channels such as the SDH/SONET transmission system or the like, if the delayed amount at the time of transmission by the communication network having the plurality of channels is greater than or equal to a predetermined time, the plurality of low capacity virtual containers divided and transmitted cannot be correctly assembled and multiplexed so as to be the plurality of original frames at the reception side, and there is the possibility of obstructing the communication.
In accordance with the consideration of the inventor of the present application, there has been increased the demands for realizing a transmission state indicating system in which, in order to carry out stable data communication via an existing wire communication network having a plurality of channels using a transmission system by the virtual concatenation technique, for example, the SDH/SONET transmission system or the like, by indicating pointer values required for evaluating the transmission state of the communication network which includes the transmission delayed amount at the respective channels and the amounts of variations due to the phase differences between the clocks of the respective channels at the plurality of low capacity channel sides and the high capacity channel at the multiplexed side, in accordance with the respective channels, as pointer values for evaluating the transmission state of the communication network having the plurality of channels, the operator can visually verify the transmission states at the respective channels and can evaluate those.